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Types of Multimedia Multimedia Combination of static and dynamic media Static Media Media that do not have time dimension Dynamic Media Media that have time dimension No time dimension - Contents do not change over time Include: Drawings, Paintings, Photographs etc. Composed of pixels Images Any character (text, white space character, control characters) Information presented clear, logical manner Alphanumeric Data System for cross linking documents / files Using links Hypertext Static Media Played constantly rate (compatible with human speech rate) If played faster or slower with compatible; - distorted Audio Combines sounds and pictures Continuous events - breaks into frames Must be played constant rate (compatible with human visual frame rate) NTSC - 30fps (525 lines) - American PAL - 25fps (625 lines) - European & Australian MPEG - must be formatted for either. Video Starts: discrete images, presents in rapid progression - impression of movement Each frame called cel Animation Dynamic Media Animation Images presented in succession at rate pf 25-30 fps Video Photography of a continous event - broken up into discrete frames Characteristics of Multimedia Systems Unit 4.2 Multimedia Systems Page 1
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Page 1: Characteristics of Multimedia Systems · Characteristics of Multimedia Systems Unit 4.2 Multimedia Systems Page 1 Output to hard copy Printing to Books, magazines etc. Difficult /

Types of Multimedia

Multimedia Combination of static and dynamic media

Static Media Media that do not have time dimension

Dynamic Media Media that have time dimension

No time dimension - Contents do not change over time •

Include: Drawings, Paintings, Photographs etc.○

Composed of pixels ○

Images•

Any character (text, white space character, control characters)○

Information presented clear, logical manner○

Alphanumeric Data•

System for cross linking documents / files○

Using links○

Hypertext•

Static Media

Played constantly rate (compatible with human speech rate)○

If played faster or slower with compatible; - distorted○

Audio•

Combines sounds and pictures○

Continuous events - breaks into frames○

Must be played constant rate (compatible with human visual frame rate)○

NTSC - 30fps (525 lines) - American○

PAL - 25fps (625 lines) - European & Australian○

MPEG - must be formatted for either.○

Video•

Starts: discrete images, presents in rapid progression - impression of movement○

Each frame called cel○

Animation•

Dynamic Media

Animation Images presented in succession at rate pf 25-30 fps

Video Photography of a continous event - broken up into discrete frames

Characteristics of Multimedia Systems

Unit 4.2 Multimedia Systems Page 1

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Output to hard copy○

Printing to Books, magazines etc.○

Difficult / log time to update○

Print Media: Static Media

Print Media Hard copy, books, magazines, newspapers etc.

DVD Digital Video Disk. Capable MPEG-2

Distributed cheaply○

Update over internet (Virus scan programs)○

DVD: single of double sided, each side 1-2 layers○

CD/DVD offer user interactivity (games, editing programs)○

CD ROM or DVD•

Content centraliased in one virtual location○

Resources may reside more one location - accessor see's website as single place○

Offers track request from customers / producers○

Internet•

Multimedia: Dynamic Media

Differences Between Print Media & Multimedia

Path followed by use different for each•

Print - Static - updates require replacement of whole copy○

Inform / Entertain through hardcopy○

Print Media:•

Displayed using screen / projector○

Stored / backup on digital device○

Multiple uses simultaneously○

Interactivity - hypertext / hypermedia○

Requires hardware and software○

Multimedia

Multimedia Hardware Requirements

Primary Storage Storage are on a memory chip or CPU that the CPU can access

Secondary Storage Storage external to direct access by the CPU

Caching Storing of particular data in primary locations, accessible by CPU

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Primary Storage

Read / Write memory○

Temporary / Volatile Memory○

Random Access Memory (RAM)•

Fixed in instructions set physical structure○

Instructions live when power is on○

Read Only Memory (ROM)•

Halfway between CPU & RAM○

Caching speeds up access frequent commands○

Instructions fetched from cache○

Slower than RAM○

When Cache & RAM are low - pc caches excess storage requirements onto disk - Disk Swapping○

Creates swap file

Paging

Process of writing excess data

As process above required continuously - written to hard drive

Whole process slowed by required read / write executions

Disk Swapping○

Cache Memory•

Since 70's○

Store up to 1.44mb○

Becoming Obsolete○

Floppy Disk•

Increase in capacity○

Sufficient of multimedia requirements○

Currently measure in GB○

Hard Disk Drive•

Alternative to Disk drives○

Sequential recording / retrieval○

Large capacity ○

Low Costs○

Tape Drive•

CD - Compact Disk

CD / DVD•

Secondary Storage

Capacity Limited ○

Capacity also increasing ○

Small form factor○

Memory Stick•

Unit 4.2 Multimedia Systems Page 3

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CD - Compact Disk○

DVD - Digital Video Disk○

Calculating Storage Requirements

Bit-Depth Number of possible colors or shades per pixel, represented by bits per pixel

Resolution The number of pixels per screen

Sample Rate Rate at which samples of an event are taken

Sample Size The size in bits of each sample taken

Still Image Storage

Variables that determine image file size:•

Bit depth (colour depth) No. bits per pixel

Total File Size Resolution x bit depth

Resolution Horizontal pixels x vertical pixel

Audio File Storage

Time dimension or length of sound piece○

Number bits per sample or size of the sample○

Sampling Rate or frequency of sampling○

Audio File Size•

Sampling

Analog data converted to digital data - sampling•

Take sample time slices of the analog signal○

Digital quality dependent upon bit size of each slice sample and sampling rate○

Large sample size greater sampling rate - better digitally converted signal○

Process: •

2x = sampling rate○

X in bits○

E.g.. 8 bits (28 = 256 colours)○

E.g.. 16 bits (216= 65536)○

Sampling Size:•

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Sampling occurred rate of one sample slice oer second - three color changes recorded○

100 samples per second - 300 color changes would be recorded○

Quality of conversation to digital data improved determined by sampling rate of conversation proses.○

Sampling Rate•

Video Data

Larger than Audio files•

Analogue Video to Digital Video undergo same sampling process as digital audio•

Video at certain speed - human compatibility - smoothness•

National Televisions Standards Committee (NTSC) - America and Japan•

Phase Alternative Line (PAL) - Australia & European Country•

Sequential Couleur a Memoire (SECAM) - France & Greece•

Video Frame Rates

Frame Single image in video or animation sequence. Consists two interlaced patterns

Half image on screen every half second.•

Every other time, other half of image is displayed•

625 lines○

50 images halves per second○

25 fps○

PAL & SECAM

525 lines○

60 image halves per second○

30 fps○

NTSC

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24 fps○

Video / Motion Picture fill speed

Frame Rate○

Running Time in Seconds○

Horizontal Size of each frame in pixels○

Vertical size of each frame in pixels○

Bit depth of each frame○

Factors to Determine size of video file

60 minutes○

25 fps○

1024 x 768 pixels○

32 bits per pixel○

E.g.. Movie

Animation Processing

Cel-Based Animation Animation techniques where each individual frame is stored separately into a memory page

Path-Based Animation Animation technique in which the only part of the frame that changes is the moving object

Tweening Generation of in-between scenes by animation software

Process of displaying series of drawn images in quick succession - effect of movement

Each drawing is a frame

Possible at 30 fps

Cel-Based○

Path-Based○

Computer Animation methods

Cel-Based Animation

Involves drawing and displaying individual frames

Storing each frame separately into - memory pages

Each sequential frame slightly different from each previous page

All frames 30 fps

Using animation software

High processing power and memory required

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Path-Based Animation

Preferred over cel based (resource equipment's can be lower)

Large part of frame remains static

Only changing part - moving object

Background may not change

Original object relocated to another part of frame

Intermediate Parts between two scenes of moving object generated with software.

Process called Tweening

Morphing - image undergoes process of metamorphosis & changes slowly from one image to completely different one

Warping - image may be stretched and resized

Fields of Expertise Required In the Development of Multimedia Applications

Content Providers - provide footage, tracks etc.○

System Designers - plan & Design System○

Project Manager - Responsibility, ensuring product delivered to client on time○

Technical Staff - graphic artist, sound engineers, layout personnel, camera operators, AV editors○

Technical Support - Skilled in hardware / software○

Design & Layout - Those who do graphic design for the presentation ○

People Involved in delivering multimedia System

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Virtual Reality

Virtual Reality

Artificial Sense Impressions, provided by programs that also exclude real;-life perceptions

Use of Computers to model and stimulate artificial environment - users immerse them selves in virtual reality

User may wear Goggles / Head Video display / Body suits•

Sensors on person detect directional movement - simulate in virtual movement•

Skiing○

Flying jets○

Etc.○

Use in games:•

Flight ○

Medical procedures○

Military training○

Use in simulations•

Education & Training

Visual displays (subtitles) help children with hearing disabilities etc.•

Capacity to be tailored to individual needs•

Individuals work at own speed and convenience •

Training programs via internet•

Training modules via CD•

Leisure & Entertainment

Greater processing power = Greater range possibilities presented to user•

Graphics more realistic•

Provide people wit =disabilities or limitations, i.e. mobility and or height•

Information

Provide users with information in different media•

Use of touch sensitive screens or actual device to view video, animation, maps etc. Listen to directions

Used to provide quantities and qualitative data in public areas i.e. Museum, Shops etc.•

Examples Of Multimedia System

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Developments in Multimedia

World Wide Web

Use in daily life•

Use in personal financial transactions•

Schools, Universities- Internet Access•

Government Set up Broadband Networks•

Compression Technologies

All multimedia files subject to compression techniques•

Barley noticeable drop in quality•

JPEG○

MPEG○

Common Compression formats:•

CD & DVD Drives

DVD Drives Optical Disk drives that read/Burn DVD's

DVD's offer greater storage capacity from 4GB - 50GB•

Fire wire IEEE - 1394a & IEEE-1394b, USB1, USB2, & USB 3

1394a Data Transfer of 400Mb/s

1394b Data Transfer of 800Mb/s

USB 1 Data Transfer of 12Mb/s

USB 2 Data Transfer of 480Mb/s

USB 3 Data Transfer of 680Mb/s

Unit 4.2 Multimedia Systems Page 9

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Displaying Hardware

Cathode Ray Tube (CRT)

CRT Uses RGB electron guns to beam electrons onto phosphor-coated screen

Consists three electron gun•

Electrons fired at a screen coated in phosphor dots•

To create an image, group of many dots once at once•

Exciting a targeted group of dots and creating an image•

Color images created by each of three electron guns firing primary color.•

Fire beam left to right, top to bottom•

This ^ Constantly repeated - phosphor glows for short time - technique (Raster Scan)•

use raster scan technique only for every second line○

Refresh rate not high enough - monitor likely to flicker○

Interlaced Monitors -•

refresh the monitor screens by scanning every line. ○

Screen changing - only changed data transmitted○

Not Interlaced Monitors -•

Liquid Crystal Display

LCD Screen uses transistors and complex chemical solution to display each pixel

Thin, Flat•

Liquid crystal layer is a crystal layer between two polarized glass sheets. Called Substrates•

Current applied to points - light passed through liquid crystal.•

Advances in LCD technology use of different variations of LCD•

Use less Power•

Smaller amounts of electrical radiation•

Size corresponds to number of pixels and transistors in manufacturer able to place the unit○

Increase in size, increase change of bad resistor○

3 Transistors required for each sub pixel (RGB)○

Problem•

Intensity of pixel controlled by voltage•

Sub pixel produce - 256 shades•

16.8 Million•

40% large LCD rejected during quality control•

Gas Plasma Displays

Displaying In Multimedia Systems

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Gas Plasma Displays

Plasma Screen Screen in which charged electrodes interact with pockets of inert gas to produce images

Creates Red, Green, Blue lights in every pixel - reducing need for space•

Charged electrodes sandwiched between two glass panels•

React with tiny pockets of inert Gas•

Gas changes to plasma, production of UV light - reacts with RGB poser in each pixel•

No electron beam•

No backlight•

Brighter, Sharper - edge to edge•

Not affected by Magnetic fields•

Free from magnetic interference•

Display unit located close to loudspeaker with out disturbance by magnetic forces•

Generate heat•

Lifespan 30,000 Hours•

Touch Screens

Sensing were user touched screen - act as mouse command•

Attached front of notebook, desktop, plasma•

Electronic whiteboards similarly•

Projection Devices

Slim line LCD panel fits above standard overhead projector - plugged onto computer○

Displayed onto light reflective surface for audience○

Data Projection Panel•

Takes output display from computer projects onto reflective surface○

Require sources greater than 1000 lumens○

Data Projector•

Require sound card from computer○

Quality depends on sound file○

Digital sound - fiber optic cable○

Audio Speakers•

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Displaying Software

Specialist Multimedia Application Software

Designed to connect best with broadband communication links •

Dealing with combination of static & Dynamic media in authoring, processing & Displaying capacities•

Allows users to create static & dynamic media○

Record final product on CD/DVD, HDD, etc.○

Authoring Software•

Allows users to make automated presentations○

Presentation Software•

Create transitions○

Titles○

Sounds○

Digital Video editing Packages•

Assist in creating / editing multimedia for WWW○

Locating and viewing material on web○

Web Browsers & Editors•

Unit 4.2 Multimedia Systems Page 12

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Compression Methods

Compression achieved by use of a codec.

Compression reduces number of bytes consumed by large files and programs

Viewing - must be decompressed

Compression Methods

Lossless Compression

Use - compression computer programs and documents, where no loss allowed i.e.. financial documents○

Only exploit data redundancies○

E.g.. GIF achieves compression ratio 2:1 - compressions: replaces repeating patterns with symbols○

Lossless Compression Algorithms that minimise redundant data and permit no reduction in some of the file data

Lossy Compression

Produce high compression ratios○

Use bot data redundancies and human perception○

Data lost in compression - might not be noticeable○

Use images on web - fast retrieval○

Quality not near original - still be conveyed to person who has retrieved it○

Unlikely to notice -reeve sound wavelengths out of spectrum○

JPEG (100:1)

MPEG 1,2

M-3 (11:1)

EG.○

Lossy Compression Algorithms that minimise redundant data and allow a reduting on some of the file data

Other Information Processes In Multimedia Systems

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Organisation of Multimedia Presentations

Scene by sconce illustration○

Linear - Sequential flowA.

Hierarchical - User chose from multiple options Top down DesignB.

Nonlinear - User allows freedom to move up to down direction within any structureC.

Combined Structure - Combination of the three structuresD.

Four types of structures○

Storyboards

Compression Methods

D

A C

B

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Identifying Multimedia File formats

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Copyright

Copyright Ownership of created work, which prohibits others using it as it were their own

Multimedia relevant - data stored in digital format (easy to locate copy & Edit)•

As technology consistently innovating around the world - patents consistently arising•

Appropriate use of Multimedia

Includes subset of legal and ethical issues•

Legal ramifications for any work published on the internet - time of writing, publisher has appeal pending

Stream and capture live video - without consent of individuals○

Privacy•

Key Logging & Screen obtaining software on PC's - obtain information remotely and display it•Placement of pornographic images - disturbing materials - place of minors, adults browsing raises legal and ethical issues

Hyperlinks of indiscriminately tempting internet users to casino websites•

Merging All Media and Communications Into One

Merging of radio, television, other modes of communication•WEB-TV - aimed at users who do not use computers•Digital TV - obtain more information from advertisements•Internet Access - internet service provider - telephone line / digital line•DSL - simultaneously receive and sends (no need for 2 telephone lines)•Higher Bandwidth to homes - more accessibility•

Data Integrity

Data Integrity

The Reliability, currency & Relevance of data

Publish Make available by distributing copes of a work as hard copy or by presenting information on the internet

Refers to reliability of data as factual, current & Relevant•Source needs to be checked and verified•

Books - formal publishing process - verified prior to publication•Internet - less formal - requirements are less, adequate knowledge•

Browsers unaware - information on website is out of date•Data integrity concern - digital signature / (login and password) legitimate / current ??•Data corrupted or tampered?•

Issues Relating to Multimedia Systems

Unit 4.2 Multimedia Systems Page 16